I have developed a system that works for me. My BG target is 115, basals about correct and insulin duration about 4 hours.
I used to take insulin as follows per my endo:
BG in the 100s - Meal bolus 15-20 minutes before eating
BG in 200s - meal bolus 20-30 minutes before eating
BG in 300s - meal bolus 30-40 minutes before eating.
These may be good guidelines for some but not for me.
Regardless of my BG I take 30U of Humalog for each meal and wait until BG falls to target and then eat 50% of carbs, then eat 25% of carbs an 1 hr later and then eat more or less than last 25% depending on BG 3 hrs after meal insulin. This works fine for breakfast and lunch as I eat lunch and dinner when I want and eat what I want. A bit more difficult for dinner as I eat when dinner is prepared but only eat 0C-5C main meal and save other 5C-15C.
Since my insulin duration is 4 hrs, I would see a big spike after eating based on endo guidelines as food duration does not match insulin duration. For me, better to eat over 3-4 hours to match insulin duration so I eat in stages but finish in 3 hrs so I have some coverage for the last hour.
My average BG has come down from 166 in August (standard deviation of 40) to 120 in November (standard deviation of 23). My goal for December is ave BG of 115 and std deviation of under 20.
In theory it seems to make sense but it can be difficult for people that don’t have CGM and must eat at specific times.
Hope this helps some of you.